How you test presence of food …

The presence of a particular component in a food item can be confirmed by performing various tests in the given sample of food.

Test for starch:

1. Take a small quantity of food item to be tested.
2. Add 2 to 3 drops of dilute iodine solution to the food with a dropper.
3. If blue-black colour is produced, then starch is present in the given food.

Test for protein:

1. Take 2 ml of the given food-stuff solution in a test tube.
2. Add a little of dilute sodium hydroxide solution till the mixture clears.
3. Then add 2 to 3 drops of copper sulphate solution and shake well.
4. If a violet colour appears in the solution, then protein is present in the given food-stuff.

Test for fats:

1. Take a small quantity of hard, solid food item and wrap it in a filter paper.
2. Crush the food item carefully by using a small hammer and rub the crushed food on the paper.
3. Remove the crushed food from the paper, and hold the paper towards a source a light.
4. Presence of oily patches on the paper shows the presence of fats in the given food item.